HTML injection via classDef SVG escape
Published May 22, 2026 · Updated May 22, 2026
HTML injection in Mermaid 10.9.5 and earlier and 11.0.0-alpha.1 through 11.14.0 allows attackers to alter pages via crafted diagrams. The state-diagram classDef path incorporates attacker-supplied style text into string-built CSS, allowing closing markup to escape the style and SVG contexts and insert DOM content. Exploitation requires a consuming application to render attacker-controlled state diagrams under the default configuration; script elements are stripped, limiting the demonstrated effect to DOM content injection and page defacement.
Summary
What happened
HTML injection in Mermaid 10.9.5 and earlier and 11.0.0-alpha.1 through 11.14.0 allows attackers to alter pages via crafted diagrams. The state-diagram classDef path incorporates attacker-supplied style text into string-built CSS, allowing closing markup to escape the style and SVG contexts and insert DOM content. Exploitation requires a consuming application to render attacker-controlled state diagrams under the default configuration; script elements are stripped, limiting the demonstrated effect to DOM content injection and page defacement.
The record
- CVE
- CVE-2026-41149
- Published
- May 22, 2026
- Updated
- May 22, 2026
- Vendor
- Mermaid
- Product
- Mermaid
- Classifications
- CWE-94
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 22, 2026CVE publishedPublication date reported by the CVE source.
- May 22, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 10.9.6
- Affected versionversion=>= 11.0.0-alpha.1, < 11.15.0
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- State-diagram classDef HTML-injection proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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